Fafnir3MM9108WITULSuper-Precision Angular Contact Ball Bearing Matched Triplex Set 40 x 68 x 15 mm, 25° Contact Angle, Light Preload, ABEC 7/9

Product Description

What this part is

A matched triplex set of super-precision angular contact ball bearings, 40 mm bore, 68 mm outside diameter, 15 mm width per bearing, with a 25° contact angle, ground faces and light preload across the set.

Decoding the designation

3MM — Fafnir super-precision series, 25° contact angle9108 — size code corresponding to the ISO 7008 envelope, 40 mm boreWI — ground-face style for matched mountingT — triplex, three bearings ground as one setUL — universal light preloadMM prefix — P4S accuracy, ABEC 7 dimensional with ABEC 9 running accuracy

What these specs mean in practice

A 25° contact angle carries more thrust and less speed than a 15° angle in the same envelope, which is what makes the 3MM series the choice for spindles with significant axial cutting load.

Three bearings ground as a triplex set share preload and load between them, giving higher axial and radial stiffness and higher combined capacity than a duplex pair of the same size. Light preload keeps heat generation and running torque at the low end of the preload range.

The WI ground-face style holds the ring faces flat and parallel so the set clamps up without shimming and reproduces the factory preload.

Quantity and configuration

Three bearings, supplied as one matched triplex set. Combined width across the set is 45 mm. Open both faces, no seals or shields.

Fitting notes

The set is mounted in the marked orientation with the face marks aligned so the ground offsets stack correctly, clamped against square ground abutment faces, and handled as a unit.

Interchange guidance

Same-spec equivalents to this set: FAG B7008-E-T-P4S-TUL, SKF 7008 CD/P4ATBTA, NSK 7008A5TRSUV3TL, RHP 7008ETTULP4. A 2MM9108WI set has a 15° contact angle and a TUM or TUH set has medium or heavy preload; both share the envelope and are related sizes.